1. Field of the Invention
The present invention relates to the field of expandable downhole tools. More particularly, the present invention relates to an expandable packer having two separate components for isolating downhole areas within a wellbore. The present invention also relates to a method for seating a packer in a wellbore.
2. Description of Related Art
The use of packers for fluidly sealing portions of a wellbore is well known. Packers are most commonly used to isolate downhole formations by sealing the annular space between a production tubing and a wellbore casing. By sealing the annulus, hydrocarbon producing zones can be isolated from other regions within a wellbore, thereby preventing migration of formation fluid or pressure between zones or behind the production tubing.
Modern packers are typically set in a wellbore through fluid activation. The packer is lowered into the wellbore on the lower end of a tubular working string. Mud or other material is then pumped down the tubular under pressure. This fluid pressure activates a seal element which is expanded to engage the inner wall of the casing.
Packers typically comprise an expandable body having a hollow interior for defining an open flow path. The expandable body includes an inner elongated hollow mandrel with a hydraulic piston movably disposed upon the external surface of the mandrel. The piston is movable between an initial xe2x80x9crunningxe2x80x9d position and a final xe2x80x9csettingxe2x80x9d position. An external sleeve is engaged by the piston when it moves between the running and setting positions. The external sleeve engages slips that expand to anchor the tool body to the well casing. A sealing element responsive to sliding movement of the external sleeve is positioned below the slips for forming a seal between the tool body and the casing at a position near the lower end portion of the tool body. The sealing element typically defines upper and lower retaining rings to fluidly seal the annulus between the tubing and the casing.
Technology for expanding packer elements against casing is disclosed in certain patents. U.S. Pat. No. 6,041,858 issued in 2000 to Arizmendi discloses a packer having two separate body sections, and a deformable material therebetween. The deformable material is extruded into the annular space between the tubing and the casing by application of a vertical force between the first and second body sections.
U.S. Pat. No. 4,753,444 to Jackson et al. (1988), discussed in the Arizmendi (""858) patent, discloses a packer having a conventional sealing element located around the outside of a mandrel. Anti-extrusion rings and back-up rings contain the seal element ends and are compressed to radially expand the seal element outwardly into contact with the well casing. Additional patents referenced include U.S. Pat. No. 4,852,649 to Young (1989), U.S. Pat. No. 5,046,557 to Manderscheid (1991), U.S. Pat. No. 5,096,209 to Ross (1992), U.S. Pat. No. 5,195,583 to Toon et al. (1993), and U.S. Pat. No. 5,467,822 to Zwart (1995).
One limitation found within conventional packers is the extent to which a secure seal can be obtained between the exterior sealing element and the interior of the casing. In this respect, a secure seal of the tubing-casing annulus is of utmost importance. As noted above, the seal is typically set through the application of fluid pressure against a piston. The effectiveness of the seal is limited by the amount of fluid pressure that can be safely applied to the packer within the working string. Thus, a need exists for a packer which can be sealed by the direct application of mechanical force on the sealing element and against the casing, without the need of fluid pressure.
An additional limitation found within conventional packers, and as noted in the Arizmendi (""858) patent, is that the exterior sealing element travels on the packer exterior from the well surface to the downhole location. When the packer is run thousands of meters into a wellbore, the packing seal abrasively contacts the interior surface of the casing. In some instances, the packing seal may be worn away from the packer sleeve. This failure may not be detected until the packer is set and the pressure containment of the isolated zone fails. Thus, a need exists for a packer which has a sealing section with a smaller outer dimension that can be run into the wellbore and then expanded. In this manner, the sealing element can be lowered into the wellbore with less abrasion of the exterior sealing element against the inner wall of the casing.
An additional disadvantage to the conventional packer is the limited diameter of the bore provided through the packer body. Those of ordinary skill in the art will appreciate that the through-opening within the inner elongated hollow mandrel defines an opening which is somewhat smaller than the interior of the casing. This creates a limitation to the size and quantity of material that can be run into the wellbore. Thus, a need also exists for a packer which accommodates a larger string of tubing, multiple strings of larger tubing, or additional electronic feedthroughs by a larger through-opening.
Accordingly, a need exists for an expandable packer that avoids the disadvantages cited above, and provides a reliable seal with the casing in the wellbore.
It is, therefore, one of the many objects of the present invention to provide a novel packer having an expandable seating body which provides a more secure fluid seal, with the seal being created by the direct application of mechanical force to the seating element against the casing.
Still further, an object of the present invention is to provide a packer body which is seated onto a seating body after the seating body has been expanded and set within the casing. In this manner, a packer body having a larger through-opening may be utilized so as to accommodate additional or larger tools therethrough.
An additional object of the present invention is to provide a packer having a seating body which is dimensioned to reduce the risk of abrasion between the sealing element and the interior casing as the seating body is run into the wellbore.
Additional objects and advantages will become apparent from the detailed description of the invention, below.
The present invention provides an expandable packer, and a method for seating an expandable packer within a cased wellbore.
The apparatus of the present invention first comprises an expandable seating body. The seating body is tubular in configuration, and is run into a cased wellbore at the lower end of a string of tubulars. The seating body is releasably connected to an expander tool. At the appropriate depth, the expander tool is activated so as to expand a portion of the seating body into contact with the casing. The connection between the expander tool and the seating body is then released. The expander tool can then be reciprocated in a rotational and vertical fashion so as to expand the entire seating body into a frictional connection with the cemented casing.
After the seating body is expanded into position, the expander tool is removed from the wellbore. A packer body is then run into the hole where it is seated onto the seating body. The inner surface of the seating body is dimensioned to receive the packer body therein.
It is one purpose of the expandable packer to provide a fluid seal between the tubing-casing annulus within a wellbore. In this manner, zones within a wellbore can be isolated. To facilitate the isolation between zones, one or more sealing elements is provided on the outer surface of the seating body. This sealing element is circumferentially fitted onto the outer surface of the seating body. The sealing element makes contact with the casing when the seating body is expanded.
In addition, one or more packer seals is provided on the packer body. The packer seals are fitted around the outer surface of the packer body. Packer seals may include chevrons, o-rings, t-seals, or bonded rubber seals, and others, and are received within and make contact with the inner surface of the seating body when the packer body is landed into the seating body.
In one aspect, the inner surface of the seating body is profiled so as to receive dogs located on the outer surface of the packer body. This provides a means for landing the packer body within the seating body. This also facilitates the removal of the run-in string without also pulling the packer body. In this respect, a shearable or other releasable connection is employed between the run-in string and the packer body so as to allow the packer body to be released from the run-in string once the packer body is seated.
In one embodiment of the method of the present invention, the packer body is run into the wellbore along with the seating body and the expander tool in a single trip.